Add scripts to roll-up basho bench results

I use this scripts to calcualte numbers for building roll-up plots.
It's a lot easier to quickly compare the results of 8 benchmarks in
one plot than it is to look at 8 plots.
Fix typos
Add script to generate gnuplot from 3 dimensions of data

By 3-dimensions of data I mean a file like so.

* a row for each benchmark (x-axis)

* a column for each system (line)

* an {x,y} cell for each value (y-axis)

benchmark       rs              yz
alpha           20295.8         70.2
india           150.6           145.5
lima            33.0            79.3
mike            38.7            114.4
november        36.5            102.8
oscar           112.3           108.3
papa            2286.8          111.2
quebec          12022.8         102.2
Add helper script to generate basho bench summary plots

This is convenient because the summary file will be named after the
directory it resides in.  That way they aren't all named 'summary.png'